diff --git a/src/blenderbim/blenderbim/bim/module/aggregate/operator.py b/src/blenderbim/blenderbim/bim/module/aggregate/operator.py
index 9ab00d205c..d09179f6b1 100644
--- a/src/blenderbim/blenderbim/bim/module/aggregate/operator.py
+++ b/src/blenderbim/blenderbim/bim/module/aggregate/operator.py
@@ -40,21 +40,22 @@ class BIM_OT_assign_object(bpy.types.Operator, Operator):
     bl_label = "Assign Object"
     bl_options = {"REGISTER", "UNDO"}
     relating_object: bpy.props.IntProperty()
-    related_object: bpy.props.IntProperty()
 
     def _execute(self, context):
+        relating_obj = None
+        if self.relating_object:
+            relating_obj = tool.Ifc.get_object(tool.Ifc.get().by_id(self.relating_object))
+        elif context.active_object:
+            relating_obj = context.active_object
+        if not relating_obj:
+            return
+
         for obj in bpy.context.selected_objects:
+            if obj == relating_obj:
+                continue
             element = tool.Ifc.get_entity(obj)
             if not element:
                 continue
-            if self.relating_object:
-                relating_obj = tool.Ifc.get_object(tool.Ifc.get().by_id(self.relating_object))
-            else:
-                if obj == context.active_object:
-                    continue
-                relating_obj = context.active_object
-            if not relating_obj:
-                continue
             result = core.assign_object(
                 tool.Ifc,
                 tool.Aggregate,
@@ -65,8 +66,6 @@ class BIM_OT_assign_object(bpy.types.Operator, Operator):
             if not result:
                 self.report({"ERROR"}, f" Cannot aggregate {obj.name} to {relating_obj.name}")
 
-        return {"FINISHED"}
-
 
 class BIM_OT_unassign_object(bpy.types.Operator, Operator):
     """Remove aggregation relationship between two ifc elements"""
@@ -164,10 +163,7 @@ class BIM_OT_add_aggregate(bpy.types.Operator, tool.Ifc.Operator):
             core.assign_object(tool.Ifc, tool.Aggregate, tool.Collector, relating_obj=aggregate, related_obj=obj)
 
     def create_aggregate(self, context, ifc_class):
-        aggregate_collection = bpy.data.collections.new(f"{ifc_class}/Assembly")
-        context.scene.collection.children.link(aggregate_collection)
         aggregate = bpy.data.objects.new("Assembly", None)
-        aggregate_collection.objects.link(aggregate)
         bpy.ops.bim.assign_class(obj=aggregate.name, ifc_class=ifc_class)
         return aggregate
 
diff --git a/src/blenderbim/blenderbim/bim/module/aggregate/ui.py b/src/blenderbim/blenderbim/bim/module/aggregate/ui.py
index d593599604..50bc8007f6 100644
--- a/src/blenderbim/blenderbim/bim/module/aggregate/ui.py
+++ b/src/blenderbim/blenderbim/bim/module/aggregate/ui.py
@@ -56,7 +56,6 @@ class BIM_PT_aggregate(Panel):
             if props.relating_object:
                 op = row.operator("bim.assign_object", icon="CHECKMARK", text="")
                 op.relating_object = props.relating_object.BIMObjectProperties.ifc_definition_id
-                op.related_object = context.active_object.BIMObjectProperties.ifc_definition_id
             row.operator("bim.disable_editing_aggregate", icon="CANCEL", text="")
         else:
             row = layout.row(align=True)
diff --git a/src/blenderbim/test/bim/feature/aggregate.feature b/src/blenderbim/test/bim/feature/aggregate.feature
index 0a2cca652f..662d3b6d15 100644
--- a/src/blenderbim/test/bim/feature/aggregate.feature
+++ b/src/blenderbim/test/bim/feature/aggregate.feature
@@ -18,10 +18,10 @@ Scenario: Disable editing aggregate
 Scenario: Assign object
     Given an empty IFC project
     And the object "IfcSite/My Site" is selected
+    And the object "IfcBuildingStorey/My Storey" is selected
     And I press "bim.enable_editing_aggregate"
     And the variable "relating_object" is "tool.Ifc.get().by_type('IfcSite')[0].id()"
-    And the variable "related_object" is "tool.Ifc.get().by_type('IfcBuildingStorey')[0].id()"
-    When I press "bim.assign_object(relating_object={relating_object}, related_object={related_object})"
+    When I press "bim.assign_object(relating_object={relating_object})"
     Then the object "IfcSite/My Site" is in the collection "IfcSite/My Site"
     And the object "IfcBuildingStorey/My Storey" is in the collection "IfcBuildingStorey/My Storey"
     And the collection "IfcBuildingStorey/My Storey" is in the collection "IfcSite/My Site"
@@ -31,8 +31,7 @@ Scenario: Unassign object
     And the object "IfcBuildingStorey/My Storey" is selected
     And I press "bim.enable_editing_aggregate"
     And the variable "relating_object" is "tool.Ifc.get().by_type('IfcSite')[0].id()"
-    And the variable "related_object" is "tool.Ifc.get().by_type('IfcBuildingStorey')[0].id()"
-    And I press "bim.assign_object(relating_object={relating_object}, related_object={related_object})"
+    And I press "bim.assign_object(relating_object={relating_object})"
     And the object "IfcBuildingStorey/My Storey" is selected
     When I press "bim.unassign_object"
     Then the object "IfcSite/My Site" is in the collection "IfcSite/My Site"
diff --git a/src/blenderbim/test/bim/test_feature.py b/src/blenderbim/test/bim/test_feature.py
index 20a48dd259..568bd48e13 100644
--- a/src/blenderbim/test/bim/test_feature.py
+++ b/src/blenderbim/test/bim/test_feature.py
@@ -18,6 +18,7 @@
 
 import os
 import bpy
+import traceback
 import webbrowser
 import ifcopenshell
 import blenderbim.tool as tool
@@ -167,10 +168,14 @@ def i_add_a_plane_of_size_size_at_location(size, location):
 @when(parsers.parse('I press "{operator}"'))
 def i_press_operator(operator):
     operator = replace_variables(operator)
-    if "(" in operator:
-        exec(f"bpy.ops.{operator}")
-    else:
-        exec(f"bpy.ops.{operator}()")
+    try:
+        if "(" in operator:
+            exec(f"bpy.ops.{operator}")
+        else:
+            exec(f"bpy.ops.{operator}()")
+    except:
+        traceback.print_exc()
+        assert False, f"Failed to run operator bpy.ops.{operator}"
 
 
 @given(parsers.parse('I evaluate expression "{expression}"'))